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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #21 Posted: Fri Sep 03, 2021 8:39 am 
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kvasir wrote:
I don't see how passing for a ko has anything to do with this if white just insists to always capture in the double-ko.

W cannot capture in double ko continuously, he will need to pass soon (allowing B to progress with the other ko, using his blocked ko advantage given by the rules). Pass for ko matters here because - with the usual interpretation - it can also be abused to make a continuous cycle (W can now take in double ko and pass for the other repeatedly, and this is forcing B do the same). This is not a problem if pass for ko only needed once for each ko, though (my third possible interpretation above).

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #22 Posted: Fri Sep 03, 2021 8:53 am 
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jann wrote:
kvasir wrote:
I don't see how passing for a ko has anything to do with this if white just insists to always capture in the double-ko.

W cannot capture in double ko continuously, he will need to pass soon (allowing B to progress). Pass for ko matters here because - with the usual interpretation - it can be abused to make a continuous cycle (W can now take ko and pass for the other repeatedly, and this is forcing for B to do the same). This is not a problem if pass for ko only needed once for each ko, though (my third possible interpretation above).


I should have made a diagram as follows:

Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------------------+
$$ | X 2 X O 1 . O X 4 X O . O X . . . . . |
$$ | X X O O O O O X X O O O O X . . . . . |
$$ | X O O X X X O X O 5 O X X X . . . . . |
$$ | 3 X X X X O X X X O O X . . . , . . . |
$$ | . . . . X O X . X O X X . . . . . . . |
$$ | . . . . X O X X O X X . . . . . . . . |
$$ | . . . . X O O O O . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


It seems to me that black can't make any progress now if white passes for :b5: because this forces black to pass for :w4:.

Click Here To Show Diagram Code
[go]$$W :w1: pass :b2: pass
$$ +---------------------------------------+
$$ | X W . O X . O X O 4 O . O X . . . . . |
$$ | X X O O O O O X X O O O O X . . . . . |
$$ | X O O X X X O X 3 X O X X X . . . . . |
$$ | X X X X X O X X X O O X . . . , . . . |
$$ | . . . . X O X . X O X X . . . . . . . |
$$ | . . . . X O X X O X X . . . . . . . . |
$$ | . . . . X O O O O . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


Black still hasn't passed for the marked stone and won't have time to do so.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #23 Posted: Fri Sep 03, 2021 8:58 am 
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Pls see my above comment: this is the traditional interpretation. But if passing for a ko is only required ONCE, B will (after one cycle) be freed from the duty of passing for the right (since both he and W already passed for both kos there, that part reverts to a normal double ko seki). Thus B will have time to progress on the left, passing for the ko there and then recapturing it (blocking for W).

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #24 Posted: Fri Sep 03, 2021 9:20 am 
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jann wrote:
Pls see my above comment: this is the traditional interpretation. But if passing for a ko is only required ONCE, B will (after one cycle) be freed from the duty of passing for the right (since both he and W already passed for both kos there, that part reverts to a normal double ko seki) and thus B will have time to cash in his blocked ko advantage on the left, after passing for the ko there and then recapturing it (blocking for W).


I may be misunderstanding. I thought what you said implied that white also could take in the double ko without passing when he has passed before. Black would be forced to take in the double ko, else this happen...

Click Here To Show Diagram Code
[go]$$W :b2: pass for the marked stone ko
$$ +---------------------------------------+
$$ | X W . O X . O X 1 X O . O X . . . . . |
$$ | X X O O O O O X X O O O O X . . . . . |
$$ | X O O X X X O X O . O X X X . . . . . |
$$ | X X X X X O X X X O O X . . . , . . . |
$$ | . . . . X O X 3 X O X X . . . . . . . |
$$ | . . . . X O X X O X X . . . . . . . . |
$$ | . . . . X O O O O . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #25 Posted: Fri Sep 03, 2021 9:27 am 
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I meant both sides become free to play in the double ko (which reverts to a normal double ko seki, after both have already passed for both kos there). But note this does not help W - B can still progress (even answering each W move on the right).

In a normal double ko seki W has infinite threats - but ko threats are useless for the left, where (after B recaptured it) W would also need to pass for the ko once before recapturing.

(EDIT: diagram) So after one cycle:

Click Here To Show Diagram Code
[go]$$W
$$ +---------------------------------------+
$$ | X O 4 O X . O X 1 X O . O X . . . . . |
$$ | X X O O O O O X X O O O O X . . . . . |
$$ | X O O X X X O X O 2 O X X X . . . . . |
$$ | X X X X X O X X X O O X . . . , . . . |
$$ | . . . . X O X . X O X X . . . . . . . |
$$ | . . . . X O X X O X X . . . . . . . . |
$$ | . . . . X O O O O . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

And :w3: cannot do anything but pass (no further pass-for-ko on the right since both sides have already passed for both kos there, and OC cannot immediately recapture :b2: because of the normal ko rule). Then after :b4:, :w5: can flip the double ko one last time, B answers, then :w7: pass (for left or just normally, doesn't matter, :b8: captures).


Last edited by jann on Fri Sep 03, 2021 10:12 am, edited 5 times in total.
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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #26 Posted: Fri Sep 03, 2021 9:52 am 
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RobertJasiek wrote:
I repeat my question for the particular position at the current moment.

Before that, let me digress a little again. That will make it unnecessary to fight your way through GT territory rules:: Honte's loops and cycles.

Let...
:w1: :b1: be ko captures / re-captures into ko-shape #1; :w2: :b2: be ko captures / re-captures into ko-shape #2; and so on...
:white: :black: be GENUINE "pass".
:wx: :bx: be "pass-for-ko" of the "traditional" J89's kind; i.e. ONE "pass" for lifting the ko-ban of ONE particular ko-shape, into which re-capturing is allowed immmediately thereafter.
:wc: :bc: be "pass-for-all-ko" of your J2003's kind; i.e. ONE "pass" for lifting the ko-bans of EVERY ko-shape, into which re-capturing is allowed immediately thereafter.
:wt: :bt: be "pass-for-ko" of the "current" J89's kind (provided my understanding is correct); i.e. ONE "pass" for lifting the ko-ban of ONE particular ko-shape, but into which re-capturing is allowed ONLY after ALL active ko-bans have been lifted before.
:b91: :w92: :b93: :w94: etc. genuine moves that do NOT capture/ re-capture into a ko-shape.

WHITE's task in the following formations is to prevent her group(s) from becoming captured. whatsoever the costs.
BLACK's task is the opposite, he has to do everything he can to capture White's group, whatsoever the costs.


+++++++++++++++++++++++++++++++

SIMPLE-ko & eye


Click Here To Show Diagram Code
[go]$$B
$$ +------------------
$$ | X Q . Q . O X . .
$$ | X X Q O O O X . .
$$ | . X X X X X X . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Black starts with :b1: .

White dreams of a cycle :w1: :b1: :w1: :b1: ..., but also knows that her dream will never become true, as the sequence :b1: :w1: (that started with Black's initial move) is forbidden by the rules.

Thus, she can only hope for a cycle :white: :black: :w1: :black: :white: :b1: ..., which would effectively result in her desired cycle above, but without breaking the rules.

Black, however, likes the sequence :white: :b91: more, with :b91: filling the ko-shape.

Please note that using :black: :white: was sufficient above.
There was NO NEED AT ALL to resort to any of :wx: :bx: :wc: :bc: :wt: :bt:.



+++++++++++++++++++++++++++++++

DOUBLE-ko


Click Here To Show Diagram Code
[go]$$B
$$ +----------------
$$ | . Y . Y O X . .
$$ | X X Y O O X . .
$$ | Q X O . O X . .
$$ | . Q O O O X . .
$$ | Q O X X X X . .
$$ | X X X . . . . .
$$ | . . . . . . . .
$$ | . . . . . . . .[/go]

Black starts with :b1: .

White already knows very well that the sequence :b1: :w1: is forbidden by the rules.
She now dreams of a cycle starting with :w2: :b2: , but has to admit that Black would never follow her, as the sequence :w2: :b2: is also forbidden by the rules.

A valid alternative for keeping her group alive is :w2: :black: :w1: :b2: :white: :b1: ...
Half the length of this cycle (= 3) is an ODD number, which means that -- in principle -- the RIGHT to initiate one of these halves alternates between both players.
Here, Black is FORCED to initiate the second half of the cycle, as :w1: was an atari (as was his initial :b1: as well). However, he might want to refrain from his second :b1:, as White played "only" a :white: before.
In order to keep the cycle going, both players must cooperate. However, none of these is forced to do so.

The other valid alternative for keeping White's group alive is :w2: :black: :white: :b2: :w1: :black: :white: :b1: ..., which effectively results in her desired sequence above, but without breaking the rules.
However, despite half the length of this cycle (= 4) being an EVEN number, cooperation between both players is also necessary to keep this cycle going, as Black will soon realise that :b2: :w1: :black: :white: is about the same as :b1: :w2: :black: :white: that did not lead to success just before, due to the symmetry of the formation. Being very well aware of this, he might not even want to start with his intial :b1: .

Please note that using :black: :white: was sufficient above.
There was NO NEED AT ALL to resort to any of :wx: :bx: :wc: :bc: :wt: :bt:.


Let's now consider what might happen when using the "path-for-ko" options mentioned above.

----------------------------------

##### :wx: :bx: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so.

In this case White -- not being aware that the formation is symmetrical -- has the option of creating the following cycle on her own:
:w1: :b2: :wx: :bx: :w2: :b1: :wx: :bx: ...

:b2: is ENFORCED, as :w1: was an atari.
:wx: enables :w2: that would be an atari.
Black is FORCED to play :bx:, in order to make :b1: possible. Otherwise, his group would become captured.

White is able to keep Black busy for a while.
But sooner or later she will realise that her ENFORCED cycle has the same effect as doing nothing. And thus will stop continuing, in order to enable a status confirmation elsewhere on the board.

Please note that half the length of this cycle (= 4) is an EVEN number. This results in the SAME player being able to start every single ENFORCED half of this cycle FOREVER.
This is the very hidden unfortunate side-effect of J89's initial version!


----------------------------------

##### :wc: :bc: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so.

In this case White -- not being aware that the formation is symmetrical -- has the option of creating the following cycle on her own:
:w1: :b2: :wc: :b1: :w2: :bc: ...

:b2: is ENFORCED, as :w1: was an atari.
:wc: enables :w2: that would be an atari.
However, :wc: also enabled :b1: . Therefore, Black is free to continue with playing a GENUINE move, as the danger of his group becoming captured after :w2: has vanished.

Half the length of this cycle (= 3) is an ODD number, which means that the RIGHT to initiate one of these halves alternates between both players.
The transition from the first half of this cycle to the second one is NOT forced. This means that the cycle is an OPTIONAL one.


Thus, Black would like the sequence :w1: :b2: :wc: :b91: more, with :b91: being tenuki.
White may be able to continue with :w2: :b1: :wc: :b93: , with :b93: being tenuki again. You you will easily recognise that White -- in principle -- simply continues with a meaningless local sequence, while Black is able to play several moves in a row elsewhere.

----------------------------------

##### :wt: :bt: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so.

In this case White -- not being aware that the formation is symmetrical -- has the dream of creating the following cycle on her own:
:w1: :b2: :wt: :bt: :w2: :b1: :wt: :bt: ...

:b2: is ENFORCED, as :w1: was an atari.
:wt: is mandatory for becoming able to play :w2: that would be an atari. However, :wt: is NOT the ONLY precondition that must be fulfilled to really being able to do so!
:bt: is mandatory for becoming able to play :b1: , if Black ever wanted to do so (but which is very hazardous to assume).
All former ko bans have been lifted, so White is able to play :w2:, starting another have of White's desired cycle, with both ko-shapes interchanged.

However, is was Black's move :bt: that FINALLY made :w2: a valid move. Black knows for sure that White is hindered to play :w2: without.
Therefore, Black likes the sequence :w1: :b2: :wt: :b91: more, as there is no danger of his group becoming captured.

By capturing once into a DOUBLE-ko, White stops herself from being able to capture into that DOUBLE-ko ever again -- in principle.
There will will be NO cycle, unless Black co-operates. Thus, such cycle will be an OPTIONAL one.



+++++++++++++++++++++++++++++++

DOUBLE-ko & LARGE eye


Click Here To Show Diagram Code
[go]$$B
$$ +--------------------------
$$ | . O . O X O . . O O X . .
$$ | O O O X X O X X X O X . .
$$ | X O X . X O O . . O X . .
$$ | . X X X X O O O O O X . .
$$ | X X O O O O X X X X X . .
$$ | O O O X X X X . . . . . .
$$ | X X X X . . . . . . . . .
$$ | . . . . . . . . . . . . .
$$ | . . . . . . . . . . . . .[/go]

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so, and play :b91: into White's LARGE eye at the right, instead.

In this case White -- not being aware that the DOUBLE-ko formation at left is symmetrical -- has the dream of creating the following cycle on her own:
:w2: :b1: :white: :b2: :w1: :black: ...
Half the length of this cycle (= 3) is an ODD number, which means that the RIGHT to initiate one of these halves alternates between both players.
Here, Black is NOT forced to initiate the second half of the cycle, as White played "only" a :white: before.
In order to keep the cycle going, both players must cooperate. However, none of these is forced to do so.

Black would like the sequence :w2: :b1: :white: :b93: :w1: :b2: :white: :b95: etc. more, in order to make sure that White understands that her one-eyed group at right could be taken off the board. Sooner or later, White will admit that continuesly re-capturing into the DOUBLE-ko only delays a result that cannot be prevented anyway.

Please note that using :black: :white: was sufficient above.
There was NO NEED AT ALL to resort to any of :wx: :bx: :wc: :bc: :wt: :bt:.


Let's now consider what might happen when using the "path-for-ko" options mentioned above.

----------------------------------

##### :wx: :bx: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so, and play :b91: into White's LARGE eye at the right, instead.

Even in this case (please note that :b91: was NO ATARI) White has the option of creating the following cycle on her own:
:w1: :b2: :wx: :bx: :w2: :b1: :wx: :bx: ...

:b2: is ENFORCED, as :w1: was an atari.
:wx: enables :w2: that would be an atari.
Black is FORCED to play :bx:, in order to make :b1: possible. Otherwise, his DOUBLE-ko group would become captured.

White is able to keep Black busy FOREVER!
Sooner or later Black will realise that the ENFORCED cycle that White initiated will make it IMPOSSIBLE to EVER return to White's LARGE eye at the right. He finally admits that White's groups are "uncapturable".

This undesirable result is a direct consequence of the very hidden unfortunate side-effect of J89's initial version!
Please note that Black would have to reduce the liberties of White's group at right to at least TWO BEFORE THE GAME STOPS, if he wanted the status confirmation declaring White's formation to be "dead".


----------------------------------

##### :wc: :bc: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so, and play :b91: into White's LARGE eye at the right, instead.

In this case White dreams of creating the following cycle on her own:
:w1: :b2: :wc: :b1: :w2: :bc: ...

:b2: is ENFORCED, as :w1: was an atari.
:wc: enables :w2: that would be an atari.
However, :wc: also enabled :b1: . Therefore, Black is free to continue with playing a GENUINE move, as the danger of his group becoming captured after :w2: has vanished.

Half the length of this cycle (= 3) is an ODD number, which means that the RIGHT to initiate one of these halves alternates between both players.
The transition from the first half of this cycle to the second one is NOT forced. This means that the cycle is an OPTIONAL one.


Thus, Black would like the sequence :w1: :b2: :wc: :b93: more, with :b93: being played into White's eye again.
White may be able to continue with :w2: :b1: :wc: :b95: , with :b95: being played into White's eye again. Sooner or later, White will understand that her one-eyed group at right could be taken off the board, and that continuesly re-capturing into the DOUBLE-ko only delays a result that cannot be prevented anyway.

----------------------------------

##### :wt: :bt: #####

Black knows from above that starting with :b1: will not lead to success. Thus, he will refrain from doing so, and play :b91: into White's LARGE eye at the right, instead.

In this case White has the dream of creating the following cycle on her own:
:w1: :b2: :wt: :bt: :w2: :b1: :wt: :bt: ...

:b2: is ENFORCED, as :w1: was an atari.
:wt: is mandatory for becoming able to play :w2: that would be an atari. However, :wt: is NOT the ONLY precondition that must be fulfilled to really being able to do so!
:bt: is mandatory for becoming able to play :b1: , if Black ever wanted to do so (but which is very hazardous to assume).
All former ko bans have been lifted, so White is able to play :w2:, starting another have of White's desired cycle, with both ko-shapes interchanged.

However, is was Black's move :bt: that FINALLY made :w2: a valid move. Black knows for sure that White is hindered to play :w2: without.
Therefore, Black likes the sequence :w1: :b2: :wt: :b93: :white: :b95: :white: etc. (with :b93: :b95: also played into White's LARGE eye at the right) more, which will easily prove that White's stones at the right can be taken off the board. White has NOT been given any opportunity to lenghten this process!

By capturing once into a DOUBLE-ko, White stops herself from being able to capture into that DOUBLE-ko ever again -- in principle.
There will will be NO cycle, unless Black co-operates. Thus, such cycle will be an OPTIONAL one.



+++++++++++++++++++++++++++++++

DOUBLE-ko & CHAIN of FALSE eyes

Click Here To Show Diagram Code
[go]$$B
$$ +--------------------------------
$$ | . O O . O . O X . X O . O X . .
$$ | O X X O O O O X X O O O O X . .
$$ | X X . X X X O X O . O X X X . .
$$ | . . . , X O X X X O O X . . . ,
$$ | . . . . X O X . X O X X . . . .
$$ | . . . . X O X X X O X . . . . .
$$ | . . . . X O O O O X X . . . . .
$$ | . . . . . . . . . . . . . . . .
$$ | . . . . . . . . . . . . . . . .[/go]

Black knows from above that he cannot kill White's group in the DOUBLE-ko directly.
Thus, he starts with :b1: capturing into the ko-shape in the upper left corner.

White knows already that the following TRIPLE-ko cycle will bail her out:
:w2: :b3: :w1: :b2: :w3: :b1: ...
( :w2: :b3: and :b2: :w3: are played in the DOUBLE-ko at right)
Half the length of this cycle (= 3) is an ODD number, which means that the RIGHT to initiate one of these halves alternates between both players.
Here, Black is NOT forced to initiate the second half of the cycle, as :w1: before was NO ATARI.

However, as he is unable to attack White's CHAIN of FALSE eyes from the inside, there is nothing else but a "pass" that he can play.
In this case, the cycle will become
:w2: :b3: :w1: :black: :white: :b1: :w3: :b2: :w1: :black: :white: :b1: ...

Please note that half the length of this cycle (= 6) is an EVEN number. This results in WHITE being able to start every single half of this cycle FOREVER.
This is the ONE AND ONLY application case that makes a SPECIAL REGULATION necessary!!!




However, instead of installing a general overall SINGLE-ko ban, the following might have been easier, more user-friendly and less prone to errors:
By the rules of status confirmation, "MOONSHINE LIFE" is declared "dead"!!!



Another proposal with the same characteristics :
Capturing into a DOUBLE-ko must never be used as a ko-threat for a SINGLE-ko during status confirmation!!!



Let's now consider what might happen when using the "path-for-ko" options mentioned above.

----------------------------------

##### :wx: :bx: #####

White's central group that is attached to Black's DOUBLE-ko group has MORE than TWO liberties!
Black knows from above that he will be unable to approach this group, in order to give atari. Thus, he declares defeat outright.

This undesirable result is a direct consequence of the very hidden unfortunate side-effect of J89's initial version!

----------------------------------

##### :wc: :bc: #####

White knows from above that he will be unable to prevent Black from approaching her central group at the upper edge, which is attached to Black's DOUBLE-ko group, so giving atari. Thus, she declares defeat outright.

----------------------------------

##### :wt: :bt: #####

White knows from above that he will be unable to prevent Black from approaching her central group at the upper edge, which is attached to Black's DOUBLE-ko group, so giving atari. Thus, she declares defeat outright.


+++++++++++++++++++++++++++++++

Your request

Click Here To Show Diagram Code
[go]$$B :w8: pass
$$ +---------------------------------------+
$$ | X X Q . Q . O X Q M O . O X . . . . . |
$$ | . X X Q O O O X Y Q O O O X . . . . . |
$$ | X X . X X X O X T Y O X X X . . . . . |
$$ | . . . , X O X X Y O O X . . . , . . . |
$$ | . . . . X O X . X O X X . . . . . . . |
$$ | . . . . X O X X O X X . . . . . . . . |
$$ | . . . . X O O O O . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

:ex: resulted from White capturing into the upper DOUBLE-ko shape with :w2: .
Black has NOT yet played a "pass" for that ko-shape.

:et: resulted from White playing a "pass" for the lower DOUBLE-ko shape.
Before, this point was occupied by :ex: , too, which resulted from Black capturing into that ko-shape with :b3: .

NOT for EACH of the ko to re-capture has been played a "pass" yet. Thus, White must not re-capture into that lower of the DOUBLE-ko shapes, where one of her stones has been captured in a ko long before.

_________________
The really most difficult Go problem ever: http://igohatsuyoron120.de/index.htm
Igo Hatsuyoron #120 (still unresolved by professionals, maybe solved by four amateurs)


Last edited by Cassandra on Fri Sep 03, 2021 10:59 pm, edited 1 time in total.
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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #27 Posted: Fri Sep 03, 2021 10:35 am 
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Cassandra wrote:
... another suggestion for you:

Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | X O . X . X O . . |
$$ | X O X X X X O . . |
$$ | . O X O O O O . . |
$$ | O O X O O O O O O |
$$ | X X O O O O O O O |
$$ | X X X X O O O X O |
$$ | . . , X X X X X X |
$$ | . X . X . . . . X |
$$ | . . . X . . . . X |
$$ +-------------------+[/go]

A snapshot from a game on the 9x9 board; komi = 7.5; no prisoners.

:b1: What do you think, has White already passed for stopping the game?

To make the suggestion clear:
:w1: As a rules expert, will you ever be asked to do a status analysis for this position?
:w2: If so, what could have been the questioner's motive?

Dear Gérard,

Apperently, the THREE questions above were too difficult? Well, here comes ONE simpler replacement:

:b2: What do you think, which of the FOUR snapshots below has been taken AFTER the respective game stopped?
(Rest of the board "pass-alive", including the visible border stones, to be clear.)

Click Here To Show Diagram Code
[go]$$B Snapshot A
$$ +---------------------------------------+
$$ | X . X O . . O X . X O . O X X ? X O ? |
$$ | X X O O O O O X X O O O O X ? X X O O |
$$ | X O O X X X O X O . O X X X X X X O ? |
$$ | . X X O X O X X X O O X O O O O O O O |
$$ | X X O O X O X . X O X X O X X X X X O |
$$ | . X O O X O X X O X X O O X ? X ? X O |
$$ | X O O O X O O O O O O O X X X X X X O |
$$ | X X X O X X X X X X X X X O O O O O O |
$$ | X ? X O O O O O O O O O O O ? ? ? ? ? |
$$ | ? X X ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | X X X ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ||[/go]

Click Here To Show Diagram Code
[go]$$B Snapshot B
$$ +---------------------------------------+
$$ | X O . O X . O X . X O . O X ? ? ? ? ? |
$$ | X X O O O O O X X O O O O X ? ? ? ? ? |
$$ | X O O X X X O X O . O X X X ? ? ? ? ? |
$$ | X X X X X O X X X O O X ? ? ? ? ? ? ? |
$$ | ? ? ? ? X O X . X O X X ? ? ? ? ? ? ? |
$$ | ? ? ? ? X O X X O X X ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? X O O O O O O ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ||[/go]

Click Here To Show Diagram Code
[go]$$B Snapshot C
$$ +---------------------------------------+
$$ | X . X O . . O X . X O . O X ? ? ? ? ? |
$$ | X X O O O O O X X O O O O X ? ? ? ? ? |
$$ | X O O X X X O X O . O X X X ? ? ? ? ? |
$$ | . X X X X O X X X O O X ? ? ? ? ? ? ? |
$$ | . X ? ? X O X . X O X X ? ? ? ? ? ? ? |
$$ | . X ? ? X O X X O X X ? ? ? ? ? ? ? ? |
$$ | X X ? ? X O O O O O O ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |[/go]

Click Here To Show Diagram Code
[go]$$B Snapshot D
$$ +---------------------------------------+
$$ | X . X O . . O X . X O . O X X ? X O ? |
$$ | X X O O O O O X X O O O O X ? X X O O |
$$ | X O O X X X O X O . O X X X X X X O ? |
$$ | . X X O X O X X X O O X O O O O O O O |
$$ | X X O O X O X . X O X X O X X X X X O |
$$ | . X O O X O X X O X X O O X ? X ? X O |
$$ | X O O O X O O O O O O O X X X X X X O |
$$ | . X X O X X X X X X X X X O O O O O O |
$$ | X ? X O O O O O O O O O O O ? ? ? ? ? |
$$ | ? X X ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | X X X ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
$$ | ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ||[/go]

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #28 Posted: Fri Sep 03, 2021 10:58 am 
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jann wrote:
I was talking about the third possible interpretation (pass for ko only needed once for each ko, for the first recapture - see above), which makes W dead here (and will likely agree with Davies / traditional interpretation in most cases, except a double ko cannot be abused in confirmation).


I believe I understand.
I tried to build an example for which this third interpretation may give a result different from J2003 but I am not completly sure.

Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | B B . O X O . O . |
$$ | B B O O X X O O O |
$$ | O O O O X . X O O |
$$ | . O O O X X O O O |
$$ | O X O O X . X X X |
$$ | X X . O X X X O O |
$$ | X O O O O O O O O |
$$ | . X O X X X X X X |
$$ | X . X . X . . X . |
$$ +-------------------+[/go]

What is the problem?
Black to play can kill all white groups => all white groups are dead.
What about black groups? All black groups are uncapturable except the four marked stones in the upper left corner.
So, the only remaining question is the following : are these four black stones alive or dead?

In J2003 they are alive due to the sequence:
Click Here To Show Diagram Code
[go]$$W :b5: ko-pass
$$ +-------------------+
$$ | B B 3 O X O . O . |
$$ | B B O O X X O O O |
$$ | O O O O X . X O O |
$$ | 2 O O O X X O O O |
$$ | 7 X O O X . X X X |
$$ | X X 1 O X X X O O |
$$ | X O O O O O O O O |
$$ | 8 X O X X X X X X |
$$ | X 6 X 4 X . . X . |
$$ +-------------------+[/go]


But what will happen with this third interpretation of the rule. It seems to me that the loop through the three ko can reappear because now white has already pass for the ko on the left => four black marked stones are dead ?

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #29 Posted: Fri Sep 03, 2021 12:09 pm 
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It's likely there are a few cases where "pass once" and "pass each time" for a ko would differ, since they are not the same thing logically. Only J89 authors could say which was meant, but it is quite possible the traditional interpretation was the correct one (for absolute ko independence, and with the double ko pass-for-ko flaw remaining overlooked).

This example seems more tricky though: this is NOT a real moonshine life, not even a combined one. W can make this into real ko fight in actual game (for triple ko draw or life with eyes). IMO an important trait of real moonshine life is that it can always be left untouched until two passes (only L/D is in question). Never a ko fight since winning such ko is impossible for one side.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #30 Posted: Fri Sep 03, 2021 12:46 pm 
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jann wrote:
It's likely there are a few cases where "pass once" and "pass each time" for a ko would differ, since they are not the same thing logically. Only J89 authors could say which was meant, but it is quite possible the traditional interpretation was the correct one (for absolute ko independence, and with the double ko pass-for-ko flaw remaining overlooked).

This example seems more tricky though: this is NOT a real moonshine life, not even a combined one. W can make this into real ko fight in actual game (for triple ko draw or life with eyes). IMO an important trait of real moonshine life is that it can always be left untouched until two passes (only L/D is in question). Never a ko fight since winning such ko is impossible for one side.


I completly agree with you Jann; "pass once" and "pass each time" for a ko would differ, and this position is not a real moonshine life.
In addition when I analyse this position with GT territory rule it is clear that the board is not black territory. The reason is quite simple; the game is not finished and white should not pass in normal play in this position.

I guess we can find a finished position with the same kind of result (a loop reappearing) but it will surely take some time to find it. ;-)

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #31 Posted: Fri Sep 03, 2021 11:11 pm 
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Gérard TAILLE wrote:
I tried to build an example for which this third interpretation may give a result different from J2003 but I am not completly sure.

Click Here To Show Diagram Code
[go]$$B
$$ +-------------------+
$$ | B B . O X O . O . |
$$ | B B O O X X O O O |
$$ | O O O O X . X O O |
$$ | . O O O X X O O O |
$$ | O Z O O X . X X X |
$$ | Z Z . O X X X O O |
$$ | Z O O O O O O O O |
$$ | . X O X X X X X X |
$$ | X . X . X . . X . |
$$ +-------------------+[/go]

It would be completely pointless to deliberately and with a vengeance construct differences between sets of rules by using positions that contain a snapshot of "eternal life" before the game stopped.

Click Here To Show Diagram Code
[go]$$W
$$ +-------------------+
$$ | X X . O X . X X O |
$$ | X X O O X X X O O |
$$ | O O O O X . X O O |
$$ | . O O O X X X O O |
$$ | O Z O O X . X O O |
$$ | Z Z 1 O X X X O O |
$$ | Z O O O O O O O O |
$$ | . X O X X X X X X |
$$ | X . X . X . . X . |
$$ +-------------------+[/go]

Probably you will realise the difference...

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #32 Posted: Mon Sep 06, 2021 7:24 am 
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jann wrote:
[...]because of the normal ko rule[...]


I see what I misunderstood.

It seems hard to find any support in the English translation for this "pass once" interpretation, but it seems to be as simple as someone just reading the Japanese.

I did also notice when checking the Japanese with google translate that it is evident that the commentary and examples have detail in the English about which ko to pass for were as the Japanese does not. There also appears to be paragraphs in the translation that are not in the Japanese, for example the first paragraph of "2. Positions Related to Article 7, Clauses 1 and 2" doesn't appear to be found in the Japanese. I refer to the version on the NHK web

It is a bit weird if the translation doesn't match the official version, but the matter really just ends there for me because it is really just a question of reading the Japanese, someone making a new translation. There doesn't seem to be anyone who claims their Japanese is very good that is pointing out errors here.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #33 Posted: Mon Sep 06, 2021 8:07 am 
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kvasir wrote:
I did also notice when checking the Japanese with google translate that it is evident that the commentary and examples have detail in the English about which ko to pass for were as the Japanese does not. ... I refer to the version on the NHK web

From the CURRENT J89 on the Nihon Kiin web:

https://www.nihonkiin.or.jp/match/kiyaku/kiyaku07-2.html


Attachments:
Image1.jpg
Image1.jpg [ 304.58 KiB | Viewed 607 times ]

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Post #34 Posted: Mon Sep 06, 2021 10:05 am 
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I mentioned this before, this would be referring to the "top corner" and the "bottom corner", but there are 2 ko shapes in the bottom corner and this is distinguished in the English translation. Just browsing through the text should be enough to see that the translation refers to ko-passes by the last move in that shape while the Japanese sometimes refers to the corner or just has an unqualified "pass".

But what is the point of us discussing interpretations of the Japanese? It is one thing to discuss the English translation but as for the Japanese original we better just wait for someone that knows Japanese very well to come along and resolve that.

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Post #35 Posted: Mon Sep 06, 2021 3:52 pm 
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kvasir wrote:
But what is the point of us discussing interpretations of the Japanese? It is one thing to discuss the English translation but as for the Japanese original we better just wait for someone that knows Japanese very well to come along and resolve that.

For now -- deep in the night -- please refer to https://lifein19x19.com/viewtopic.php?p=267226#p267226 ("old" translation matches the CURRENT Japanese text).

More on J89's commentary section is to come in bright daylight :razz:

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #36 Posted: Tue Sep 07, 2021 3:55 am 
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Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------+
$$ | X O a . X O . . . . . . . |
$$ | . X X X X O . . . . . . . |
$$ | X X O O O O . . . . . . . |
$$ | O O O , . . . . . , . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . , . . . . . . |
$$ | X X X X X . . . . . . . . |
$$ | O O O O X . . . . . . . . |
$$ | X O . O X . . . . , . . . |
$$ | . X O O X X . . . . . . . |
$$ | X X X O O X . . . . . . . |
$$ | . X O . O X . . . . . . . |
$$ +---------------------------+[/go]

A comparison of the translation by James Davies at the time and a translation of the CURRENT version of the comments on the combined formation of a "one-move approach-move-ko" and a "double-ko seki" makes it easy to see what has been adjusted in the meantime.


James Davies' translationTranslation of CURRENT version
3. Approach-move ko with double-ko seki (example of capturing again after passing for that particular ko capture).3 It is necessary to pass for each of the ko to be recaptured.
./.If there are two or more ko to be recaptured, it must be specified which one to pass for.
Suppose positions in Diagram 11 are both present on the board. The question is whether the game can end without Black's playing at A.(1) If the shapes of the upper and lower corners coexist on the board, it is the question of whether or not the game can end without any Black teire at A in the "One-move yose-ko" in the upper corner.
The answer: If the game ends in this way, the white stone is dead despite the double ko in the position at the right. Black does not have to add a stone at A.(2) If the game ends as it is the conclusion is even if there is a "double-ko seki" in the lower corner, the white stone in the upper corner is a "dead stone", the black eight stones there are "alive stones", and the lower corner remains the same1) "double-ko seki"; therefore, Black doesn't need to teire at A.
The reason the white stone is dead is as follows.
White 1 takes ko (on left) and Black 2 passes because recapturing is prohibited except after passing. White 3 gives atari. Black 4 retakes ko, a legal play because Black has passed once for this ko (in lieu of Black 2). White 5 takes a ko on the right and Black 6 takes the other ko. White 7 passes for the left ko, because recapturing without first passing is prohibited.
Black 8 captures two white stones on the left. White 9 and Black 10 pass for kos on the right. White 11 takes ko; this is legal because White has passed at play 9. Black 12 takes ko; this is legal because Black has passed at play 10.
Note that if White 7 was a pass for the ko 6/11 on the right, Black could have played 8 at 12 and captured the white group on the right. White could still not capture on the left and that Black group would remain alive.
(3) The reason is based on White 1 to Black 12 in Reference Figures 11 <2> to <4>. It is possible to make a new ko-capture with Black 4 in Reference Figure 11 <3> because Black 2 has already passed for the same ko.
Black 2 upper corner pass
White 7 upper corner pass, White 9 lower corner pass, Black 10 lower corner pass


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1) This "same" might be the reason for having an entire double-ko cycle in the sequence.

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #37 Posted: Wed Sep 08, 2021 5:15 pm 
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Your translation and James Davie's are quite different but it is hard to find a "misinterpretation".

It is interesting that example 18 is different (which was pointed out in another thread), I'd say "The plot thickens", but are we to understand that you are working on a new translation?

I'd say that the words that you quote from the translation have some bearing on the ongoing discussions in this and the other threads.

Quote:
The question is whether the game can end without Black's playing at A.


This can be interpreted to mean that during confirmation (this is actually exactly what I learned when I learned how to play and my experience when playing Japanese persons) the object is not to resolve some bestiary like mutual-death and surprise ko fights but to fill in dame and add defensive moves that could have been added during normal play but the Japanese like to omit. Defensive moves during confirmation are only mentioned in the examples of confirmations, not the rules themselves, but are we not to conclude from this that the players are allowed to make these defensive moves after plays ends and before the "end of the game" (i.e. during confirmation).

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Post #38 Posted: Thu Sep 09, 2021 12:30 am 
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kvasir wrote:
Quote:
The question is whether the game can end without Black's playing at A.

This can be interpreted to mean that during confirmation (this is actually exactly what I learned when I learned how to play and my experience when playing Japanese persons) the object is not to resolve some bestiary like mutual-death and surprise ko fights but to fill in dame and add defensive moves that could have been added during normal play but the Japanese like to omit. Defensive moves during confirmation are only mentioned in the examples of confirmations, not the rules themselves, but are we not to conclude from this that the players are allowed to make these defensive moves after plays ends and before the "end of the game" (i.e. during confirmation).

Very interesting experience. Thank you for sharing it.

What you wrote about some Japanese fondness, seems to be backed by J89's commentary on Article 9, "End of the game":


Article 9, clause 2: After the game is stopped, and both sides confirmed the life and death of the stones and the territory, the game ends by agreement. This is called "end of the game".

<Commentary>

1 "Dame-occupation" and "teire" are necessary
In order to confirm the life and death of the stones and the territory according to Article 8, "dame-occupation" and "teire" must be made until the end of the game.

2 After the game has stopped, "dame-occupation" and "teire" are outside regulation
With the agreement of the players, if "dame-occupation" and "teire" is appropriate after the game stopped, they do not fall under the prescribed regulations for "move".



The Japanese understanding of the matter seems only natural, as it makes a FORMAL resumption of the game superfluous in potentially "critical" L&D cases. Which would be possible, as the players have not yet agreed about ending the game. As potential unwanted side-effects of necessary, but still unplayed, "teire" exist during confirmation of L&D ONLY (due to "pass-for-ko"), but not during "play", it will not have any negative effect to have the opponent re-continuing the "normal" game (not unlikely with a "pass").

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Post #39 Posted: Fri Sep 10, 2021 1:06 pm 
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J89's Life and Death Example 18:: "Bent-Four and IRREMOVABLE KO-THREAT"!!! ==> "Dead"


Click Here To Show Diagram Code
[go]$$B
$$ +---------------------–-
$$ | . O . X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | . X O O O X X O O . .|
$$ | X X O O . O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O X . X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

The double-ko seki at right can easily lead us on the wrong track, because it is part of this example ONLY because of its quality as a ko-threat that cannot be eliminated.

This example is NOT (!!!) "Bent-Four and Double-Ko Seki", as we will see soon.


+++++++++++++++++++++++++++

Let's examine what would happen during "play".

Click Here To Show Diagram Code
[go]$$W :b2: pass
$$ +---------------------–-
$$ | 1 O 3 X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | 4 X O O O X X O O . .|
$$ | X X O O . O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O X . X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:w1: attack's Black's bent-four in the corner.

Click Here To Show Diagram Code
[go]$$W
$$ +---------------------–-
$$ | 6 5 . X O X O . . . .|
$$ | 7 X X X O X O O . . .|
$$ | X X O O O X X O O . .|
$$ | X X O O . O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O X . X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:b6: avoids a quick death.
:w7: gives atari at Black's corner group.

Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------–-
$$ | 3 O a X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | X X O O O X X O O . .|
$$ | X X O O 1 O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O X 2 X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:b8: gives atari in the double-ko. This is the IRREMOVABLE KO-THREAT!!!
:w9: also captures in the double-ko.
:b10: recaptures in the corner.
This move would NOT be valid during J89's status confirmation, Black would have to play a "pass-for-ko", instead, whereafter White would capture with A.

Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------–
$$ | X O 5 X O X O . . . .|
$$ | b X X X O X O O . . .|
$$ | X X O O O X X O O . .|
$$ | X X O O X 4 X X O , .|
$$ | O O O . O X 6 X O . .|
$$ | X X O O a O X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:w11: gives atari at Black's double-ko group again.
:b12: Black captures White's single stone in the corner, achieving a living shape for his former bent-four.
We will leave "chôsei" (i.e. :b12: at A, :w13: at B, ...) aside for a while, as it would only lead us astray in this L&D example.
:w13: captures Black's double-ko group.

Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------–
$$ | X . X X O . O . . . .|
$$ | . X X X O . O O . . .|
$$ | X X O O O . . O O . .|
$$ | X X O O . O . . O , .|
$$ | O O O . O . O . O . .|
$$ | X X O O . O . . O . .|
$$ | . X X O O . . O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

White was unable to capture the entire corner.

--------------------------------

Variation:

Click Here To Show Diagram Code
[go]$$Bm8
$$ +-----------------------
$$ | . O 2 X X X O X O . .|
$$ | O X X X O O O X O . .|
$$ | X X X O O X X X O . .|
$$ | X X O O 1 O X X O , .|
$$ | X X O 3 O X . X O . .|
$$ | X X O O X a X X O . .|
$$ | X X X O O X X O O . .|
$$ | X X X O X O O O . . .|
$$ | O O O O X X X X . . .|
$$ | X X X X X . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:w9: would capture Black's corner group, if it was much larger.
During J89's status confirmation, White would capture with A in the double-ko.
:b10: captures through.

Click Here To Show Diagram Code
[go]$$Bm8 :w11: pass
$$ +-----------------------
$$ | . O O . . . O X O . .|
$$ | O . . . O O O X O . .|
$$ | . . . O O X X X O . .|
$$ | . . O O X . X X O , .|
$$ | . . O X 5 X . X O . .|
$$ | . . O O X . X X O . .|
$$ | . . . O O X X O O . .|
$$ | . . . O X O O O . . .|
$$ | O O O O X X X X . . .|
$$ | X X X X X . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

:w11: can only pass.
:b12: Black connects the ko, achieving a living shape for his double-ko group.

Click Here To Show Diagram Code
[go]$$Bm8
$$ +-----------------------
$$ | . O O . . . O X O . .|
$$ | O . . . O O O X O . .|
$$ | . . . O O X X X O . .|
$$ | . . O O X . X X O , .|
$$ | . . O X X X . X O . .|
$$ | . . O O X . X X O . .|
$$ | . . . O O X X O O . .|
$$ | . . . O X O O O . . .|
$$ | O O O O X X X X . . .|
$$ | X X X X X . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]

Again, White was unable to capture the entire corner.

In status confirmation, Black would prefer this variation, as :b12: is played AFTER his corner group has been captured, providing that group with the status "alive", too.
As we have already stated above, J89's status confirmation would never reach this point.

--------------------------------

You will have realised that White can capture only ONE of both Black groups during "play". Thus, we could anticipate the entire corner becoming a large seki during status confirmation, similar to J89's L&D example 4, if left untouched.

However, Japanese understanding prohibits "real" ko-fights during J89's status confirmation, overriding the results achieved above.
Thus, the entire corner will become White's territory.



+++++++++++++++++++++++++++


Click Here To Show Diagram Code
[go]$$W
$$ +---------------------------+
$$ | . O . X O X . O O O O O O |
$$ | O X X X O X . O O O O O O |
$$ | . X O O O X X X X X X X X |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

Same topic, different position.

--------------------------------

Click Here To Show Diagram Code
[go]$$W :b2: pass
$$ +---------------------------+
$$ | 1 O 3 X O X . O O O O O O |
$$ | O X X X O X . O O O O O O |
$$ | 4 X O O O X X X X X X X X |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

:w1: attacks Black's bent-four at the left.

Click Here To Show Diagram Code
[go]$$W
$$ +---------------------------+
$$ | 6 5 . X O X . O O O O O O |
$$ | 7 X X X O X . O O O O O O |
$$ | X X O O O X X X X X X X X |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]


Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------------+
$$ | . O 2 X O X 3 O O O O O O |
$$ | O X X X O X 1 O O O O O O |
$$ | X X O O O X X X X X X X X |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

:b8: gives atari at the right. This is the IRREMOVABLE KO-THREAT!!!
:w9: captures at the left here.
:b10: captures at the right.
During "status confirmation", this move would provide the captured group at the left with the status "alive".

Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------------+
$$ | . O O . O X X . . . . . . |
$$ | O . . . O X X . . . . . . |
$$ | . . O O O X X X X X X X X |
$$ | . . O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

White could not capture all of Black's groups.

--------------------------------

Variation:

Click Here To Show Diagram Code
[go]$$Bm8 :w11: pass
$$ +---------------------------+
$$ | 3 O 5 X O X 2 O O O O O O |
$$ | O X X X O X 1 O O O O O O |
$$ | X X O O O X X X X X X X X |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

:w9: captures Black's group at the right.
White would choose this line of play in J89's status confirmation.
:b10: Black recaptures at the left.
This move would be unvalid in J89's status confirmation. Black would have to play a "pass-for-ko", instead, whereafter White would capture with :w12: .
:w11: can only pass.
:b12: achieves a living formation.
Again, Black's captured group (here that at the right) would also be "alive" during status confirmation.
J89's status confirmation would NOT reach this point.

Click Here To Show Diagram Code
[go]$$Bm8
$$ +---------------------------+
$$ | X . X X O . O O O O O O O |
$$ | . X X X O . . O O O O O O |
$$ | X X O O O . . . . . . . . |
$$ | X X O X X O O O O O O O O |
$$ | O O O X O O . . . . . . . |
$$ | . . X X O . . . . . . . . |
$$ | X X X O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]

Again, White could not capture all of Black's groups.


+++++++++++++++++++++++++++


You will have realised that the double-ko seki in J89's L&D example 18 is NOT an element of this example in its capacity as a double-ko seki as such.
The formation in example 18 probably looks a little less improbable than the one I created.

You will also have understood that "bent-four & irremovable ko-threat" would become seki in status confirmation without any special regulation that prohibits the flare-up of ko-fights.

_________________
The really most difficult Go problem ever: http://igohatsuyoron120.de/index.htm
Igo Hatsuyoron #120 (still unresolved by professionals, maybe solved by four amateurs)

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 Post subject: Re: J89's pass-for-ko: Misinterpreted in the Western Go Worl
Post #40 Posted: Fri Sep 10, 2021 3:59 pm 
Lives with ko

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Click Here To Show Diagram Code
[go]$$W
$$ +---------------------------+
$$ | . 7 . 4 3 2 . 1 1 1 1 1 1 |
$$ | 5 4 4 4 3 2 . 1 1 1 1 1 1 |
$$ | . 4 3 3 3 2 2 2 2 2 2 2 2 |
$$ | 4 4 3 6 6 O O O O O O O O |
$$ | 3 3 3 6 O O . . . . . . . |
$$ | . . 6 6 O . . . . . . . . |
$$ | 6 6 6 O O . , . . , . . . |
$$ | O O O O . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . , . . , . . , . . . |[/go]


I don't think this is controversial or unexpected:
:w1: seki, :b2: seki, :w3: alive, :b4: dead, :w5: alive, :b6: dead, :w7: alive


But in example 18 it appears that unless pass-ko is limited (for example as Jann suggests) it is unclear why the marked stone is dead.

Click Here To Show Diagram Code
[go]$$B
$$ +---------------------–-
$$ | . O . X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | . X O O O X X O O . .|
$$ | X X O O . O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O Y . X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]


Why is it not alive like this, maybe your translations can shed light on this somehow.

Click Here To Show Diagram Code
[go]$$W :b4: pass :w5: pass
$$ +---------------------–-
$$ | 1 O . X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | . X O O O X X O O . .|
$$ | X X O O 2 O X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O X 3 X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]


Click Here To Show Diagram Code
[go]$$B :b3: pass :w4: pass
$$ +---------------------–-
$$ | O O . X O X O . . . .|
$$ | O X X X O X O O . . .|
$$ | . X O O O X X O O . .|
$$ | X X O O X 2 X X O , .|
$$ | O O O . O X . X O . .|
$$ | X X O O 1 O X X O . .|
$$ | . X X O O X X O O . .|
$$ | . . X X X O O O . . .|
$$ | . . . . X X X X . . .|
$$ | . . . , . . . . . , .|
$$ | . . . . . . . . . . .|
$$ | . . . . . . . . . . .|[/go]


Black appears to always be able to play at :b1: again because of the pass-ko.

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